The invention relates to an apparatus for the coating of the surfaces of a workpiece with a spray gun for the thermic depositing of surface layers.
Flame spraying is a thermic surface coating process for metallic but also non-metallic workpieces. For such a process a flame spraying gun may be utilized, for example, as described in the specifications DVS 2307, 2301.
A combustible gas (usually acetylene which must not be pressurized to more than 1.5 bar), an ignition gas (usually hydrogen), oxygen and powder are combined in a predetermined ratio and a flame jet is formed therefrom, which is directed onto a cleaned and dried surface. The spray material (powder) may consist of metallic or nonmetallic materials as described in DIN-Proposal 32529 and DIN specifications 55928 and 8566, part 2. The thermal energy necessary for the melting of the coating material is obtained either autogenously or electrically.
So far, flame spraying has been utilized only under normal atmospheric conditions. Fields of application are the flame spraying of surfaces in ship building and of off-shore structures as corrosion protection of areas above water level. There is, however, no indication that surface coating by flame spraying would be possible below the surface of the water, under higher than atmospheric pressures or in situ in wet environment. With the flame spraying equipment known so far the process could not be performed under those conditions since no flame would be sufficiently effective. The main object of the present invention nevertheless is to provide an apparatus which permits providing of metallic or non-metallic surfaces with metallic or non-metallic coatings by flame spraying in dry as well as in higher than atmospheric or wet environments with or without higher than normal pressures.